Out on the street near the Doyles' home, there was some commotion. Looking out, they could see it was the police.

Elaine's mum asked a detective what was going on and he told her a girl's body had been found. She knew the dead girl was her daughter.

The half-naked body was found in a lane only 25 yards from her home in Ardgowan Street. Someone had pounced on her, stripped her, sexually assaulted her and strangled her.

Word spread through Greenock fast. Around the cops' scene of crime barrier, people gathered - young people, tears streaming down their faces. They had just lost a wonderful friend.

Strathclyde Police put out appeals for information from anyone around the scene at that time. That's when the poor bloke came forward.

Just after midnight, near Ardgowan Street, he had seen a young woman with a man walking behind her. They were having angry words.

He had spoken to them, trying to make sure she was OK. He had been told to go away. So he did, thinking it was just a lovers' tiff.

Was that Elaine and her killer? Could he have saved her life? The man would carry the regret for the rest of his life.

Over the next weeks, the cops visited 1300 homes, took more than 3000 statements and spoke to thousands more people. It wasn't getting themanywhere.

In time, they would approach notorious murderers such as Gavin McGuire and serial sex killer Robert Black since he had spent some of his early adulthood in Greenock and might well have come back. Both were ruled out.

Years went by and there was no breakthrough in the investigation. But the cops had a secret or two up their sleeves.

Elaine had not been raped. Stripped and sexually assaulted but not raped.

A certain type of sex killer would behave like that. Maybe a sex killer who was impotent.

The second secret was the most important. Only police and her parents knew that her blue leather bag was missing.

A week after the murder, it mysteriously turned up on the steps of Watt Monument Library. The police didn't want to reveal that since the killer might have left it there.

Or maybe some witness who knew more about the murder. Someone had tried to burn that bag and failed.

But there were secrets in that bag even the killer didn't know about - mysterious red head hairs.

In 1986, head hair was useful in ID parades. The police knew that DNA was being worked on and, at some time in the future, head hairs might identify the only person in the world they could belong to.

So the hairs were kept secret and stored for future use.

What kind of killer takes a trophy from his victim? What kind of killer torments cops by laying the bag out to be found? A very dangerous killer and one who might strike again.

The years ticked by and Elaine's murder remained unsolved. Then in 2006, cops announced they were actively working on the case again.

All the paperwork was being fed into the HOLMES computer used in complex cases these days. It would be a long, painstaking job but it would be worth it.

DNA checks were to be run on everyone who gave statements in 1986. It would take time to track all these people down. But it would be worth it.

The police were openly saying that the murder would be solved in the future. Of course, there are also those few red head hairs in storage.

Back in 1986, one of the biggest gathering of teenagers in Greenock's history took place. It was Elaine Doyle's funeral.

Those grief-wracked young faces have now grown into adulthood without their much-loved friend.

One day soon, they may be able to lay a little of their grief to rest - when they are told who killed their guardian a ngel.